KR100577655B1 - Catalyst Support - Google Patents

Abstract

A catalyst support structure e.g. for use in an ammonia oxidation reactor, comprising a series of primary supports (19) disposed above a catalyst bed, a lattice assembly disposed beneath the catalyst bed and on which the catalyst bed rests, said lattice assembly being suspended from the primary supports (19) by suspending means (27) extending through the catalyst bed. Preferably the support structure includes a static start-up burner arrangement in the form of one or more perforated tubes (24) adjacent the primary supports (19).

Description

Catalyst Support {Catalyst Support}

The present invention relates to a support catalyst for reactions carried out at relatively high temperatures in the production of nitric acid by oxidation of catalyst supports, in particular ammonia.

In the ammonia oxidation process thus far, a lattice of steel beams, often along with other precious metals such as palladium, often in the form of metals or piles of wire mesh or catalyst in the form of bundles are placed across the reaction vessel under the catalyst bed Is supported on the image. Under normal operating conditions, a reactant, for example a gaseous mixture of ammonia and air, is supplied to the vessel space above the catalyst, usually at elevated temperatures of 100 to 300 ° C. A strong exothermic reaction occurs when passing through the catalyst, and the gas temperature typically increases rapidly to a temperature of 800 to 950 ° C. Thus, the support grid is exposed to such high temperatures. The diameter of the reaction vessel is usually 2 to 6 m, and thus of relatively closely spaced steel beams of considerable depth, usually 15 to 30 cm, extending across the vessel to withstand the high temperatures while supporting the catalyst without excessive deformation. Lattice was generally an essential structure. Such structures are expensive because they must be made of materials that are heavy and can withstand harsh operating conditions. Typically, the grating has a welded "bottle basket" structure. Such an arrangement is not only heavy and expensive, but also susceptible to bending and damage, and is difficult and expensive to repair due to the welded structure.

The inventors have finally recognized that if the primary support is on top of a catalyst layer in which the prevailing conditions are not so severe, it is possible to use a support structure which is much lighter and thus cheaper and easier to handle.

Accordingly, the present invention includes a lattice assembly having a series of primary supports extending across the vessel and a catalyst layer disposed under the primary support and suspended from the primary support by means of suspending extending through the catalyst layer. Characterized in that there is provided a structure for supporting a catalyst layer in a vessel.

The invention is explained with reference to the accompanying drawings.

1 is a schematic vertical cross section through an ammonia oxidation reactor.

2 is a plan view of the reactor with the upper shell member removed.

3 is a cross-sectional view taken along line III-III of FIG. 2.

4 is a plan view of the base assembly with the primary support member assembly and cover plate removed from FIG.

5 is an isometric view of a portion of the base assembly.

FIG. 6 is an enlarged plan view of a portion of FIG. 2 showing four base assemblies and grid assemblies supported thereby; FIG.

7 is an elevation view of a portion of the grid assembly.

8 is a cross-sectional view taken along the line VIII-VIII in FIG. 7, showing the adjacent grid assembly in dotted lines.

9 is a cross sectional view of a portion of a skirt illustrating a method of supporting a grid assembly at a vessel wall.

10 is a top view of the arrangement of FIG. 9.

11 is a view similar to the bottom of FIG. 3, showing yet another embodiment.

FIG. 12 is a view similar to FIG. 10 showing a method of supporting the grid assembly at the container wall as another embodiment.

FIG. 13 is a view similar to FIG. 8, showing yet another embodiment.

FIG. 14 is a view similar to FIG. 3 showing another starting combustor arrangement.

FIG. 15 is a view similar to FIG. 14 showing another starting combustor arrangement.

Referring to FIG. 1, the ammonia oxidation reactor consists of an outer shell of generally circular cross section formed as upper and lower shell members 10, 11 provided with reactant inlet 12 and reaction product outlet 13, respectively. The upper shell member is provided with a perforated diffuser plate 14 extending across the shell. The diameter of the reactor is usually about 4 m.

The lower shell member has a skirt 15 positioned around the inside of the container by an outwardly extending flange seated in the groove 16 of the upper rim of the lower shell member 11. The skirt 15 has an upper cylindrical portion and an inward tapering, ie a cone portion 17. Since the lower part of the skirt is likely to be much hotter, for example at about 900 ° C., than the lower part, which is usually at about 300 ° C. during operation, the conical structure allows a slight difference in thermal expansion of the lower part of the skirt to the upper part do.

As shown in FIG. 2, a large number of channel segmentation supports 18 are welded on top of the conical portion of the skirt in pairs arranged chordally. Typically, there are five pairs of supports 18. Each pair of channel partition supports has a primary support member 19. This primary support member has a lattice assembly, and because the primary support member is located above the catalyst bed, it is placed in a relatively cold part of the reactor and therefore does not need to be made of a material that can withstand the high temperatures encountered at or below the catalyst bed. . The primary support member may be hollow or empty and may have any convenient cross section. However, the primary support member is preferably a pipe because pipes of suitable material and size are readily available. The number, structure and size of primary support members required will depend on the size of the reactor and the load to be supported. Typically, when the reactor diameter is 4 m, five primary support members in the form of pipes of about 10 cm diameter spaced about 80 cm apart may be used.

The grating assembly comprises a number of base assemblies 20 connected by pairs of grid supports 21 and a number of grid assemblies 22 (only one in FIG. 2 is shown) carried by the grid supports 21. As will be explained below, the grid support 21 is attached to the lower cone structure portion 17 of the skirt member 15.

A large number of base assemblies 20 are suspended from each primary support member 19. Typically these assemblies are arranged in a square structure at a pitch corresponding to the spacing of the primary support members 19. The catalyst layer (indicated by dashed line 23 in FIG. 1 and only a portion in FIG. 2) is disposed on top of the base and grid assembly. It is preferable, but not necessary, that the base assembly 20 is arranged in a square pattern, and thus may be arranged in another structure, for example a rectangular or triangular pattern.

Although the base and grid assemblies are located in the high temperature region of the reactor, the load on the individual assemblies is relatively small. In particular, there are no individual underload members extending across the entire width of the reactor in the high temperature region, and thus no large structure is needed to withstand large deformation loads. Thus, the amount of high temperature resistant material is reduced.

In a conventional ammonia oxidation reactor, the reaction is initiated by heating the catalyst bed by means of a rotary combustor which directs the flame obtained by burning the combustible gas, for example hydrogen, onto the catalyst bed, whereas in the present invention such a structure has such It is not suitable because it needs to be placed on the primary support member and the primary support member is brought into contact with the localized high temperature upon initiation by the combustor.

In the present invention, this problem is overcome by providing a static starting combustor arrangement in the form of one or more tubes adjacent to the primary support member and means for providing combustible gas thereto. The tube or tubes are provided with perforations (not shown) at intervals such that the flame can be directed downwardly, preferably outward, onto the catalyst bed. As shown in FIGS. 1, 2 and 3, the combustor may comprise an S-shaped single tube 24 adjacent to the primary support member 19. For clarity in FIG. 2, some of the entirety of these sigmoidal tubes are shown, some of which are indicated by dashed lines. Fuel gas, for example hydrogen, may be supplied to the sigmoidal tube 24 via a suitable inlet pipe 25, indicated by the dashed line in FIG. 2.

2 and 3, an S-shaped tube 24 is supported on a pedestal 26 located at the suspending point of each base assembly. For clarity in FIG. 2, the pedestal 26 is shown only at the position where the sigmoidal tube 24 is shown in solid lines. As shown in FIG. 3, the pedestal 26 and the base assembly 20 are supported by a coupling rod 27 from the primary support member 19. While this coupling rod will withstand the load and be at a high temperature at its lower end, the coupling rod is under tension and therefore does not suffer a load that deflects. For adjustment in the assembly of the entire catalyst support structure, the placement of the base assembly 20 relative to the primary support member 19 is preferably adapted to the threaded portions and nuts at the upper and / or lower ends of the coupling rods 27. Is made by

The base assembly 20 is shown in more detail in FIGS. 3, 4 and 5. The base member 28 and the cover plate 29, which are preferably castings, which eliminate the need for welding, are supported by respective joining bars 27. When the base assembly 20 is arranged in a square or rectangular structure, each base member 28 preferably has an octagonal structure and has inner and outer upstands 30, 31 arranged in pairs. . In the case of a square or rectangular structure of the base assembly 20, each base member 28 has four pairs of upstands.

Each external upstand 31 is provided with a slot 32 through its wall. The inner and outer upstands are provided with two pairs of notches 33 on their top surfaces (see FIG. 5). At each pair of notches 33 is located a hinge member 34 having a rounded projection 35 engaged with the notch. Thus, each hinge member 34 can pivot with respect to the inner and outer upstands. When assembled, the cover plate 29 of the base assembly 20 acts as a latch that holds the protrusion 35 of the hinge member 34 at the notch 33 of the upstand.

In addition, each hinge member 34 is provided with a pin 36 protruding from the hinge member 34 in a direction perpendicular to the axis of the rounded projection 35 and located below the axis of the projection 35. Grid supports 21 with slots 37 drawn at each end are mounted on each pin 36 and extend through slots 32 of the outer upstand 31. Thus, the grid support is supported by the pins 36 on the hinge member 34 that pivot about an axis above and perpendicular to the pins 36 at the base member 28. Thus, the grid support 21 extends from the base member 28 in a direction parallel to the axis of the round protrusion 35. Each grid support 21 is engaged at its other end with a pin connected around the lower portion 17 of the corresponding pin or skirt 15 on the hinge member of the adjacent base assembly. Mounting the grid support around the skirt is described below with reference to FIG. 9.

The grid support 21 is moved freely in the longitudinal direction with respect to the base member 28 by the elongated slot 37 and freely shaken laterally by the hinge member 34 to move the grid support 21 laterally. To make it possible. Since each pair of notches 33 in the upstands 30, 31 carries a hinge member 34, and each hinge member 34 carries a grid support 21, the base assemblies 20 are connected to each other. It is connected by pairs of grid supports 21 that are spaced apart and move freely laterally and longitudinally relative to each other. Thus, the base assembly 20 and thus the coupling rods 27 are not subjected to heat induced lateral stresses, thus minimizing the force of tendency to bend.

Referring to FIG. 6, four adjacent base assemblies 20 are connected by pairs of grid supports 21. Grid assembly 22 is located on each pair of inner grid supports. The grid assembly includes an outer octagonal ring member 38 dimensioned to expand through thermal expansion without imposing excessive force on adjacent grid assemblies and base assemblies 20 on another grid support of the grid support pairs. . To prevent welding, the ring member 38 may simply have a bent metal structure. The ring member 38 is provided with a downwardly extending projection 40 which serves to position the grid assembly with respect to the grid support 21. Thus, the expansion of the ring 38 causes the grid support 21 to move longitudinally and laterally, but the hinge member 34 and the elongated slot 37 at the ends of the grid support 21 as described above. Due to the mounting of the grid support 21 through it, such longitudinal and lateral movements do not generate a force which causes the base assembly 20 and the coupling rod 27 to bend.

As shown in FIGS. 6, 7 and 8, the opposite face of the ring member 38 is provided with a number of notches on its top face. In a pair of opposing faces, the notch 41 acts to support the grooved crossbar 42 having a notch 43 supporting the rod 44. The distal end of the rod 44 is located in the notch 45 of the pair of other opposite faces of the ring member 38. The top surface of the crossbar 42, the rod 44 and the ring member 38 is preferably substantially coplanar with the top surface of the cover plate 29. Notches, grooves on rods 42, and the length of crossbars and rods are dimensions such that relative movement can accommodate thermal expansion. The number and spacing of the rods and crossbars will depend on the acceptable "sag" of the catalyst layer disposed on the grid assembly. In general, as described below, the wire mesh 46 is disposed on top of the grid assembly to act as a support between adjacent crossbars and rods. Typically, the spacing between adjacent cross bars and the spacing between adjacent bars is 2 to 15 cm, in particular 3 to 12 cm. It will be appreciated that the spacing between adjacent cross bars 42 does not necessarily have to be the same as the spacing between adjacent bars 44.

9 and 10, a grid support 21 is mounted around the skirt. In FIG. 10, the wire mesh 46 is omitted for clarity. The pedestal 47 is welded to the lower conical portion 17 of the skirt in the required position. The pair of hinge members 48 are pivoted at each pedestal about an axis parallel to the length of the grid support 21 by a hinge pin 49. Each hinge member 48 has a pin 50 extending laterally from the hinge member but vertically away from the hinge pin 49. Each pin 50 is engaged with a slot 37 elongated at the end of the associated grid support 21. It will be appreciated that the ring member adjacent the perimeter of the skirt will be shaped to fit the grid support 21 and the area enclosed by the skirt.

By arranging the hinge members 34, 48 to pivot at positions above the pins 36, 50 supporting the grid supports 21, the grid supports 21 are in the lowest position when the assembly is assembled at ambient temperature. There will be a tendency, and the difference in thermal expansion will result in the pivoting of the hinge members 34, 48 with lateral movement accompanied by slight elevation of the grid support 21. Thus, upon cooling and retraction of the assembly, the hinge member will tend to return to its lowest position.

In another embodiment as shown in Figures 11, 12 and 13, a simple structure may be used in which the hinge member is omitted. In this embodiment, each grid support 21 is a notch shaped protrusion 51 protruding at each end engaged in a slot or notch 52 extending in the outer upstand 31 of the base member 28. Internal upstand is omitted. Similarly, around the skirt, the projections 51 engage the slots or notches 53 at the pedestals 47 fixed to the lower portion 17 of the skirt. Thus, the grid support 21 freely expands longitudinally and moves laterally in the slots 52 and 53. In this embodiment, the octagonal ring member is omitted and the crossbar 42 is mounted to the notch 54 of the top surface of the grid support 36. At the distal end of the crossbar 42 is provided a notch 55 that engages the notch 54 of the grid support. Thus, upon thermal expansion or contraction of the crossbar 42, the grid support 21 moves laterally in the slots or notches 52, 53. By notch 55, upon cooling and retracting, the grid support tends to return to the original position where it was cooled.

The entire support assembly simply has a base member 28 (having a joining rod 27 extending therefrom) on a suitable substrate and a skirt 15 (channel partition support 18 and flanges welded or otherwise fixed thereto). It will be understood that it can be configured by supporting (with 47). The grid support 21 (and hinge members 34, 48, if used) is then located on the base member 28 and the flange 47. An octagonal ring 38 (if used) is then placed on the crossbar 42 and the grid support 21 located at the appropriate notches 41 or 54. The rod 44 is then placed in the notch 43 of the crossbar 42, and after the cover plate 29 is placed, the wire mesh 46 having holes at regular intervals relative to the engagement rod 27. It is mounted on this rod 44 and the cover plate 29. The wire mesh preferably extends over all areas of the skirt in a single piece and can be secured around it, for example by welding if desired. Subsequently, a catalyst, which may be a bundle or particles of the metal net, is disposed on the net 46. Then, the pedestal 26, the S-shaped tube 24 and the primary support member 19 are disposed on the coupling rod 27, and the primary support member 19 is seated in the channel partition support 18. . Subsequently, after the nut 56 (see FIG. 3) is applied to the upper end of each coupling rod 27, the skirt 15 supporting the entire assembly can be lifted and placed in the reactor.

In the above embodiment, the catalyst layer is heated to the ignition temperature by burning the gas supplied through the sigmoidal tube 24. This allows all catalyst beds to be heated simultaneously, but this arrangement can present practical difficulties in that a relatively large amount of fuel gas, for example hydrogen, is required. Another arrangement is to heat the sections of the catalyst bed in turn. This allows a large number of individual tubes parallel to each primary support member, with means for separating each tube from the gas supply, except where it is desirable to heat the compartment of the catalyst bed under the tube. Can be achieved by substituting

In another arrangement, the primary support members can be disposed radially instead of being arranged parallel to each other, thus providing a compartment of the grating assembly free from the coupling rods. In this case, the primary support members can fall perpendicular to each other so that they cross over each other at the center of the device. In this way, the need for a welded joint member at the center can be avoided. The initiating heater can then be in the form of a plurality of radially extending combustor tubes having a plurality of perforations arranged such that the flame can be directed downwardly from the tube or tubes to the catalyst bed, and the radially extending combustor tube between the connecting rods. Means are provided for vibrating about the longitudinal axis of the device under the primary support member across the compartment. The radially extending combustor tube is supplied with fuel gas from a central supply pipe.

Another preferred starting combustor arrangement is shown in the embodiment of FIGS. 14 and 15. In the arrangement of FIG. 14, which is a view similar to the arrangement of FIG. 3, where the base assembly 20 is shown in dashed lines, the sigmoidal tube 24 and its support pedestal 26 are omitted and the coupling rod 27 is It is hollow for part of the length. Radial holes 57 are drilled at suitable locations on the catalyst bed to communicate with the hollow interior 58 of the binding rod 27, thus providing a combustor orifice. To start, the fuel gas, for example hydrogen, is supplied to the upper end of the hollow interior 58 of the coupling rod by means not shown and flows down through the hollow interior of the coupling rod and is ejected through the combustor orifice, in which the orifice It burns to provide a flame that heats the catalyst bed.

It will be appreciated that the binding rod may be a tube having a plug or plug suitable for its lower end. In addition, each coupling rod may consist of compartments of a hollow rod lower compartment and an upper tubular compartment, for example, which may be welded together or screwed together.

In the arrangement of FIG. 15, which depicts just the upper portion of the coupling rod assembly, but similar to FIG. 14, on the catalyst bed each coupling rod is provided with a hollow cylinder provided with a perforation 60 and a fuel gas supply line 61 in a suitable position to form a combustor orifice. A combustor assembly in the form of a hermetic enclosure in the form of a casing 59 is provided.

In the arrangements of FIGS. 14 and 15, it will be appreciated that if desired, the combustor orifice may be tilted to direct the flame down onto the catalyst bed. If the base assembly 20 and the coupling rods 27 are arranged in a square configuration as in FIG. 2, each coupling rod will be provided with four combustor orifices facing towards the coupling rods arranged diagonally opposite the square structure. Can be. In addition, it will be appreciated that in some cases it may not be necessary to provide combustor arrangements for all of the coupling rods, for example, a combustor arrangement may be provided for the coupling rods that are filtered one by one. Suitable igniters such as spark plugs (not shown) may be provided to perform ignition of the fuel. Since the flame can be transferred from one combustor to another, there is no need to provide such ignition means for each combustor.

As mentioned above, the catalyst may be a bundle of a network or a net of platinum alloyed with a noble metal, for example rhodium, or a particulate catalyst such as rare earth / cobalt as described in WO 98/28073 of the inventors. It may be a fixed layer of the oxide composition.

Claims (21)

A lattice assembly having a series of primary supports extending across the vessel and a catalyst layer disposed under the primary support and suspended from the primary support by means of suspending means extending through the catalyst layer. Structure for supporting the catalyst layer. The structure of claim 1, wherein the primary support extends in a string shape across the vessel. The structure of claim 1, wherein the grating assembly comprises a plurality of base assemblies and a plurality of grid assemblies supported by the grating assembly. 4. The structure of claim 3, wherein the base assembly is suspended from the primary support by the coupling rods. The structure of claim 4 wherein the base assembly is disposed in a square structure. 5. The base assembly of claim 4, wherein the base assembly comprises a base member supported by the base members and connected by pairs of grid supports capable of moving longitudinally and laterally relative to each other and to the base member. Structure. 7. The structure of claim 6, wherein the grid support is supported by the pin on a hinge member that pivots about an axis perpendicular to or above the pin at the base member. The structure of claim 6, wherein the grid assembly is supported by an inner grid support of each pair of grid supports connecting adjacent base members. 10. The structure of claim 8, wherein the grid assembly comprises a member extending across an area surrounded by the inner grid support and freely moving in the longitudinal direction. 10. The system of claim 9, wherein the grid assembly includes a ring member engaged with the inner grid support, wherein the member extending across an area surrounded by the inner grid support is located in a notch on the top surface of the loop member. Structures. 10. Structure according to any one of the preceding claims, characterized in that the catalyst layer comprises a bundle of nets or nets of precious metals. 10. Structure according to any one of the preceding claims, characterized in that the catalyst layer comprises a granular fixed bed of rare earth / cobalt oxide composition. The structure of claim 1, wherein the primary support member is disposed radially. 14. A static starting combustor arrangement according to any one of claims 1 to 10 and 13, in the form of one or more perforated tubes adjacent to the primary support, and means for supplying combustible gas to the tubes or tubes. And the perforation of the tube or tubes is arranged such that the flame can be directed downward on the catalyst bed from the tube or tubes. 15. The structure of claim 14, wherein said combustor comprises a single perforated tube disposed adjacent said primary support in an S-shaped structure. 16. The structure according to any one of claims 1 to 10, 13 and 15, wherein the suspending means comprises a coupling rod, at least some of which are provided with an initial combustor arrangement. 17. The structure of claim 16, wherein at least a portion of the coupling rod is hollow and has radial holes and means are provided for supplying fuel gas inside the hollow coupling rod. 17. The structure of claim 16, wherein at least some of the coupling rods are provided with enclosures provided with combustor orifices surrounding the coupling rods for at least a portion of their lengths and provided with means for supplying fuel gas to the enclosures. 14. The apparatus of claim 13, having the form of a plurality of radially extending combustor tubes, wherein each tube has a plurality of perforations arranged such that sparks can be directed downward from the tube or tubes to the catalyst bed. And a means for oscillating the radially extending combustor tube under the primary support member about the longitudinal axis of the apparatus. 20. The structure according to any one of claims 1 to 10, 13, 15 and 17 to 19, wherein the primary support is supported by a skirt member positioned around the inner circumference of the container. . 21. The structure of claim 20 wherein the lower portion of the skirt member has a truncated cone structure and a grating assembly is attached to the lower portion at regular intervals.

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